'77 85hp Johnson surges, stopped..

[LiLGrady17]

This is the first time I had the boat out this year. Did a bunch of work over that last two years on the engine, & was so looking forward to an 'un-eventfull' boating season.. Yeah RIGHT!

(new WP impeller, carbs rebuilt, new fuel line & ball, new starter, Seafoam decarb, timing checked -Joe Reeves Method, Link-N-Sink, new plugs, replaced lower unit oil, new batteries & a cable)

Launched the boat, started right up.. As we were headed out the creek, I noticed some more exhaust smoke than usual, but, figured, since I've been running the engine on the muffs so much, there was probably alot of oil caked in the exhaust housing.. Once I made the entrance, I throttled up, exhaust cleared to normal.... It hit 4500-5000 right away, we got up on plane. Then the engine started to surge, up to 54-5600, then drop off to 44-4500, then recover.. First thing I thought of was the old gas' ethenol absorbed some water over the winter & throttled back a bit. I brought the boat around & started in. I explained to my guest the situation, then the rpms started dropping off.. until the engine stopped.. I noticed some steam/white smoke now coming out of the cover.. I pulled the cover, the engine was felt really hot. The engine never seized, I could crank it over the whole time. I set my anchor & called a friend for a tow..The the rain started.. Once I was back at the house, I was able to start the engine on the muffs. As I walked around back, I saw steam, which I assumed was the rain steaming off, but then I saw bubbles from the back side of the port head, near the exhaust!
I ran for the ignition switch & shut it down.. I hosed the rest of the boat off, packed up my electronics, then hit the fridge for a brew! I need it..

Where do I start?

 

[gabriel charest]

Re: '77 85hp Johnson surges, stopped..

start to do a compression test... sound like you burn a piston...

 

[LiLGrady17]

Re: '77 85hp Johnson surges, stopped..

Wet compression test, throttle held open, plug wires grounded.

2-140 1-130
4-125 3-130

The plugs look fine. Found the plastic clamp on the port (2-4) head had let go. I'm suspecting the head wasnt getting the propper cooling.
I've re-installed the plugs and am going to get some fresh gas & see how it runs off the can.

 

[iwombat]

Re: '77 85hp Johnson surges, stopped..

I think you got it nailed. If the bubbles you're talking about were bubbling paint, you probably want to just go ahead and replace the port head gasket, and check the head for any kind of warping. If it were mine, I think i'd do it anyway.

 

[jonesg]

Re: '77 85hp Johnson surges, stopped..

I would also install a temp guage, its very simple and cheap enough to do.

You did the water pump but what about the thermostats?

It think overheated due to something. Then blew the gasket.

 

[LiLGrady17]

Re: '77 85hp Johnson surges, stopped..

Ok. I find I need OMC 318662 for the head gasket, and OMC 318335 for the cover gasket. I'd like to get them from iBoats to support the site, but can't find those numbers. Anyone have any updated numbers on these? Thanks!

 

[iwombat]

Re: '77 85hp Johnson surges, stopped..

I wouldn't worry about the cover gasket. Just do the head gasket and call it a day.

 

[LiLGrady17]

Re: '77 85hp Johnson surges, stopped..

I would also install a temp guage, its very simple and cheap enough to do.

You did the water pump but what about the thermostats?

It think overheated due to something. Then blew the gasket.

I know there was some reason for the overheat. I'm guessing the ethanol could have caused a lean/hot burn along with the insufficient cooling from the hose clamp being broken, allowed the head to get way too hot..
I'll search for installing a temp gauge. I plan on doing the add a telltale too..

The thermostat will be a project. The bolts to the housing are rusty nubs, unrecognizable as bolts... The best idea I came up with was grinding all the nubs off, then removing the housing. Then soak the studs with penetrating oil & use vise grips to spin the headless studs out. Any other ideas on the Thermostat?

 

[iwombat]

Re: '77 85hp Johnson surges, stopped..

If you can remove the houseing and the bakeolite spacer just put a torch to 'em and use the vicegrips. You'll have to look around for another set of bolts though. If you want the OEM treated bolts they're getting to be fairly rare.

 

[LiLGrady17]

Re: '77 85hp Johnson surges, stopped..

Ok, Thanks.. Can I use stainless bolts for replacement?
Also, I've seen mentioned in other head gasket repairs replacing the water restrictiors. What are these, the hose I see in the block jacket?

 

[LiLGrady17]

Re: '77 85hp Johnson surges, stopped..

Ok, pulled the head. The gasket looks broken down, cant tell if if from removing it, or seeping, but it needs replacement. Also, the bolts didn't feel to have all the same torque when I removed them though, with the 'loosest' right where I saw the bubbles so I'd say this could be a contributing problem as well. After cleaning, I mounted a piece of sandpaper on a flat surface & did the figure 8 pattern. The 8 outer bolt tabs contacted, the 2 bolt pad areas adjacent to the cylinders show no sanding marks so I need to try the head up a bit. Also, as for gaskets, the one I removed was OMC 318662. The OMC 318358/GLM33540 looks exactly the same. Original 318662s are $18-49 dollars as compared to $11-13. Can I use it instead?

How does the lower cowling come off/down? Do I need to unbolt all the fasteners I can see on the top, or can I undo the horizontal bolts on the front of the leg & just undo the bolts attached to anything off the power head on the top to let it drop down??